Power drill with lubricator



April 9, 1968 J. HOLZAPFEL POWER DRILL WITH LUBRICATOR Filed May 4, 1966 mQ KN ,r MN R na wmm lnventar:

a on W la Q m.

J o M w a w \Mtd United States Patent 3,376,939 POWER DRILL WITH LUBRICATOR Jakob Holziipfel, Calw, Wurttemberg, Germany, assignor to Friedrich Duss Maschincnfabrik, Neubulack, Kreis Calw, Wurtternberg, Germany Filed May 4, 1966, Ser. No. 547,460 Claims priority, application Germany, May 7, 1965, D 47,190 9 Claims. (Cl. 173116) The present invention relates to a machine tool.

More particularly, the present invention relates to a lubricating system for manually guided, electrically driven power drills for working stone of the type described in applicants copending application Ser. No. 312,375 filed Sept. 30, 1963, now Patent No. 3,256,944. Such drills are provided with an axially vibratable drilling tool whose vibratory movement is brought about by the stroke of a piston which is arranged in a cylinder and which is driven by means of a crank drive. The piston acts on the drilling tool via an air cushion and a mass which is arranged in the cylinder for engaging the tool, and is reciprocated therein by this air cushion. Accordingly, such drills have many movable parts which must be lubricated in order to assure a long useful life span for the drill.

In accordance with the present invention, it is an object thereof to provide a lubricating system for lubricating the movable parts of the power drills of the above described type.

It is another object of the present invention to provide a lubricating system for power drills of the aforementioned type which has a simple construction and which lubricates all of the movable parts of the drill automatically and reliably.

It is a further object of the present invention to provide a lubricating system for such power drills in which the operation of the lubricating system is essentially independent of the spatial position of the power drill.

With the above objects in view, the present invention resides, basically, in a motor driven power drill of the above described type in which the air cushion which is disposed within the cylinder between the freely positioned mass element and the piston of the crank drive is periodically placed in communication by means of at least one air-passage valve with the drill housing and is also placed in communication with an oil reservoir such that pressure minima occurring in the air cushion chamber cause an oiLpassage valve for the oil reservoir to be periodically opened, oil then being introduced into the air cushion.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a view, partly in longitudinal section, of a power drill according to the present invention.

FIGURE 2 is a sectional view taken on line 22 of FIGURE 1.

FIGURE 3 is an enlarged view, partly in longitudinal section, of the oil reservoir and valve of the embodiment of FIGURE 1.

FIGURE 4 is an enlarged view, partly in longitudinal section, of a modification of the oil reservoir and valve shown in FIGURE 3.

FIGURE 5 is a cross-sectional view of a portion of the lubricating system according to the present invention.

Referring now to the drawings, there is shown in FIG- URE 1 a power drill according to the present invention, having disposed within a cylinder 1 an axially, freely positioned mass element 2 and a driving piston 5 which is hingedly connected to a crank drive formed by elements 3 and 4. As shown, the crank drive is coupled to a motor 30 via a suitable gearing arrangement 15 and 16 for reciprocally driving the piston 5. The piston 5 and the mass element 2 serve for defining the location of an air cushion 6 within the cylinder 1 and arranged therebetween. The cylinder 1 is provided with openings such as bores 7 and 8 so that the portion of the cylinder having the air cushion located therein may be vented, i.e., be placed in communication with the interior 26 of the housing of the power drill, each of these openings forming a part of an air-passage valve.

The air-passage valves also include a control shaft 31 which, as will be described below, coacts with the openings 7 and 8 so that when the shaft 31 is in the position illustrated in FIGURE 1, the air cushion 6 is vented. In the illustrated embodiment, the bores 7 and 8 place the air cushion in communication with the space 26 which is enclosed by the drill housing. The shaft 31, is, as illustrated, arranged in the housing of the power drill and is oriented parallel to the cylinder 1. The shaft is hollow and is driven by the motor 30 via a gear train formed by gears and shafts 10 through 16. The shaft 31 carries two tubular rollers 9 which are axially so positioned that the outer ends of these rollers are aligned with the openings 7 and 8 in the cylinder 1. As shown in FIGURE 2, the walls 9' of the rollers 9 are provided with notches 9a, arranged about the circumference of the walls such that during rotation of the shaft 31, the air cushion 6 is periodically vented when the notches 9a communicate with the openings 7 and 8 and the chamber is closed when the walls communicate with the openings 7 and 8.

In practice, the transmission ratio of the gear train for the shaft 31 is such that the openings 7 and 8 will be periodically closed in synchronism with the stroke of the piston 5.,Accordingly, the mass element 2 oscillates within the cylinder 1 in synchronism with the pressure variations within the air cushion caused by the movement of the piston 5 and periodically strikes the drill tool 32 for providing the same with an axial stroke. The movements of the mass element and the driving piston provide an efiect such that not only the volume, but also the location of the air cushion 6 within the cylinder is constantly varied. Furthermore, the arrangement is such that the air-passage valves are opened and closed in synchronis m with the movement of the crank drive for the piston 5 such that the valves are predominantly closed during the return stroke of the piston.

As shown, an oil reservoir 23 is connected to the cylinder 1 by a conduit means in the form of a connecting line 22 which opens into the cylinder via an oil-passage valve. The line 22 terminates approximately in the center of the cylinder 1 so that the oil reservoir 23 is periodically in communication with the air cushion 6 as it oscillates within the cylinder. As shown in FIGURE 3, the oil-passage valve is disposed at the inlet of the connecting line 22 into the oil reservoir and comprises a valve body 19 which is biassed by a spring 20 against a valve seat 21 which is formed in the wall of the oil reservoir 23. The initial tension of the spring 20 is so proportioned that the valve body will be lifted only a few microns from the seat 21 when pressure mini-ma occur within the air cushion 6 thereby creating a suction eliect on the valve. The connecting line 22 is provided with a radial bore 24 in close proximity to the oil-passage valve for communicating with the interior 26 of the housing. In addition to this bore or for selective operation with the bore, the oil reservoir 23 may be placed in communication with the atmosphere or the interior of the housing by means of a unilaterally acting valve, not shown, which isvpreferably disposed within the locking screw for the reservoir and serves to compensate for any possible reduction in pressure within the reservoir. A group of pins 27 is positioned within the oil reservoir against the inlet to the connecting line 22. These pins are embedded in a bore of the wall of the oil reservoir asshown in FIGURE 5. The arrangement is such that the interstices between the pins form capillaries which are filled with oil at all times, even when the oil level in the reservoir 23 is low, and in this manner always convey the oil to the connecting line 22.

In FIGURE 4 there is shown a modified embodiment of the arrangement of FIGURE 3 for conveying oil to the connecting line 22. A flexible end section 22 of the connecting line 22 projects into the oil reservoir and a weight 25 is secured to the free end thereof. Thus, the flexible end section is arranged within the oil so that oil may be received into the connecting line 22 for any spatial position of the drill.

The operation of the lubricating system is such that oil from the reservoir 23 flows to the movable portions of the power drill in essentially the following manner. During the movement of the driving piston 5 and the mass element 2, the air cushion 6 oscillates in the cylinder 1 and is subjected to pressure variations, the pressure variations coinciding with changes in the volume of the air cushion. Thus, on the forward stroke of the piston 5, pressure maxima are produced in the air cushion 6 and the arrangement is such that the openings 7 and 8 are closed by the valve rollers 9 in synchronisrn with the movement of the piston 5 so that these openings are predominantly closed during the return stroke of the piston and open during the forward stroke. In the illustrated embodiment, the air-passage valves are in each case closed in the rearward most position of the crank drive and are open in the forward most position. The return stroke of the piston produces pressure minima in the air cushion 6 and the period of maximum valve closure coincides approximately with this interval of maximum reduced pressure within the air cushion.

Accordingly, pressure fluctuations occur in the air cushion and due to the opening of the connection line 22 into the air cushion, these pressure fluctuations are propagated into the connecting line 22 and result in axial movement of the spring-loaded valve body 19. When pressure maxima occur, the valve body 19 is forced against the valve seat 21 whereas when pressure minima occur, these minima produce a suction effect in the connecting line 22 and cause the valve body 19 to be lifted a few microns from the valve seat so that trace amounts of oil from the oil reservoir 23 are suctioned into the connecting line 22. The trace amounts of oil oscillate in the connecting line 22 in the form of oil droplets under the influence of the presusre fluctuations. The specific control of the venting of the openings 7 and 8 in the cylinder assures that the motion component of the oil in the connecting line 22 toward the cylinder 1 is greater than the movement being inversely directed since these openings are predominantly closed during the return stroke of the driving piston. In other words, at the time when the pressure mimina are being produced, the section etfect is only propagated in the line 22 whereas, when the pressure maxima are formed in the air cushion the openings 7 and 8 are predominantly in the open condition so that the pressure maxima are also propagated into the interior 26 of the housing. Thus, the pressure minima have a stronger influence on the connecting line 22 than the pressure maxima. It should be noted that the opening 24 and the connecting line 22 can not compensate for the pressure minima occurring in the air cushion 6 whereas, on the other hand, this opening causes a reinforcing of the transport of the oil in the connecting line toward the air cushion 6 by reason of the fact that air is additionally drawn in behind the oil and thereby forces the oil into the air cushion chamber.

As a result of the varying intensity of the influence of the pressure maxima and rninima, as described above, the trace amounts of oil in the connecting line 22 pass into the air cushion 6. In the air cushion, the oil is subjected to the occurring pressure maxima and minima so as to cause a fine dispersion of the oil into the various portions of the power drill. This dispersion process is enhanced by the high frequency of the pressure fluctuations which may, for example, be on the order of 2,000 fluctuations per minute.

Since, during a portion of the movement of the air cushion, the air cushion is temporarily in communication with the interior 26 of the housing by means of the openings 7 and 8, attenuated pressure variations are also propagated into this chamber. As a result thereof, the oil mist is distributed over the entire housing chamber which is open to all parts of the power drill which require lubrication. Also, the cylinder portion in front of the mass element 2 is formed with radial bores (not shown) such that the oil mist in the interior of the housing passes through these bores into the portion 18 of the cylinder 1 which is positioned in front of the mass element 2. In this manner, the oil can pass into the mounting for the tool 32 and thereby also lubricate this moving portion of the power drill.

Thus, in accordance with the present invention, oil from the chamber 23 is automatically and reliably dispersed throughout the power drill to all of the movable parts thereof and lubricates the same. Due to the suction effect produced in the air cushion, the oil is conveyed from the reservoir to the air cushion in any position of the power drill, i.e., whether the drill is in a horizontal or vertical position. Thus, the life time of the drill is increased since all movable parts are subject to lubrication during operation of the drill.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A power drill assembly for working stone and including a lubricating system, said assembly comprising, in combination, a housing having arranged therein: an axially vibratable drilling tool; means for vibrating said tool in the axial direction thereof and including a cylinder, a freely movable mass slidably arranged in said cylinder and engaging said tool, a piston also slidably arranged in said cylinder and being axially spaced from said mass thereby to form an air cushion between said mass and said piston, a crank drive for reciprocating said piston in said cylinder, a drive motor for driving said crank drive so that on the forward stroke of the crank drive pressure maxima are produced within the air cushion and on the return stroke pressure minima are produced within the air cushion; at least one air-passage valve arranged for coacting with said cylinder for periodically lacing that portion of said cylinder in which said air cushion is located in communication with the interior of the drill housing; an oil reservoir; and conduit means communicating with that portion of said cylinder in which said air cushion is located and said oil reservoir, said conduit means having an oil-passage valve located therein which valve is periodically opened by the pressure minima occurring in the air cushion for permitting transport of oil from the oil reservoir into the air cushion.

2. A power drill assembly as defined in claim 1 wherein said motor opens and closes said air-passage valve in synchronism with the movement of the crank drive such that during the return stroke of the driving piston that portion of the cylinder in which the air cushion is located will be at least predominantly closed so that it will not be in communication with the interior of the drill housing.

3. A power drill assembly as defined in claim 2 wherein the opening and closing of the air-passage valve is controlled so that the valve is closed in the most rearward position of the crank drive and is opened in the forward most position of the crank drive, the period of maximum valve closure substantially coinciding with the 5 period of maximum reduced pressure within the air cushion.

4. A power drill assembly as defined in claim 3 wherein said air-passage valve comprises at least one bore through said portion of said cylinder in which said air cushion is located, valve element means rotatably mounted outside of the cylinder for coacting with said bore for periodically closing the same, and drive means coupled to said motor for rotating said element means.

5. A power drill assembly as defined in claim 1 wherein said oil-passage valve comprises a valve seat 'formed in a wall of said oil reservoir, a valve element, and a spring for biassing said element in a direction towards said valve seat which biassing direction is opposite to the direction of the oil passage.

6. A power drill assembly as defined in claim 5 wherein said conduit means is provided with at least one radial opening arranged between the air cushion and the oil reservoir.

7. A power drill assembly as defined in claim 6 further comprising an element having capillaries therein, said element being disposed in said oil reservoir at the inlet 6 to said conduit means for conveying oil in said reservoir to said conduit means.

8. A power drill assembly as defined in claim 5 wherein said conduit means is provided with a flexible end portion which projects into the oil reservoir and having a weight secured to the free end thereof.

9. A power drill assembly as defined in claim 1 and further comprising means for placing that portion of said cylinder which is in front of said mass and the interior of the drill housing in communication for permitting the passage of oil into such portion.

References Cited UNITED STATES PATENTS 1,829,609 10/1931 Robinson 173-116 2,024,684 12/1935 Erfass 173-116 3,161,242 12/1964 Etzkorn et al. 173-109 3,170,523 2/1965 Short 173-104 JAMES A. LEPPINK, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,376 ,939 April 9 1968 Jakob Holz apfel It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, line 4, "Neubulack" should read Neubulach Signed and sealed this 14th day of October 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

1. A POWER DRILL ASSEMBLY FOR WORKING STONE AND INCLUDING A LUBRICATING SYSTEM, SAID ASSEMBLY COMPRISING, IN COMBINATION, A HOUSING HAVING ARRANGED THEREIN: AN AXIALLY VIBRATABLE DRILLING TOOL; MEANS FOR VIBRATING SAID TOOL IN THE AXIAL DIRECTION THEREOF AND INCLUDING A CYLINDER, A FREELY MOVABLE MASS SLIDABLY ARRANGED IN SAID CYLINDER AND ENGAGING SAID TOOL, A PISTON ALSO SLIDABLY ARRANGED IN SAID CYLINDER AND BEING AXIALLY SPACED FROM SAID MASS THEREBY TO FORM AN AIR CUSHION BETWEEN SAID MASS AND SAID PISTON, A CRANK DRIVE FOR RECIPROCATING SAID PISTON IN SAID CYLINDER, A DRIVE FOR RECIPROCATING SAID PISTON DRIVE SO THAT ON THE FORWARD STROKE OF THE CRANK DRIVE PRESSURE MAXIMA ARE PRODUCED WITHIN THE AIR CUSHION AND ON THE RETURN STROKE PRESSURE MINIMA ARE PRODUCED WITHIN THE AIR CUSHION; AT LEAST ONE AIR-PASSAGE VALVE ARRANGED FOR COACTING WITH SAID CYLINDER FOR PERIODICALLY PLACING THAT PORTION OF SAID CYLINDER IN WHICH SAID AIR CUSHION IS LOCATED IN COMMUNICATION WITH THE INTERIOR OF THE DRILL HOUSING; AN OIL RESERVOIR; AND CONDUIT MEANS COMMUNICATING WITH THAT PORTION OF SAID CYLINDER IN WHICH SAID AIR CUSHION IS LOCATED AND SAID OIL RESERVOIR, SAID CONDUIT MEANS HAVING AN OIL-PASSAGE VALVE LOCATED THEREIN WHICH VALVE IS PERIODICALLY OPENED BY THE PRESSURE MINIMA OCCURRING IN THE AIR CUSHION FOR PERMITTING TRANSPORT OF OIL FROM THE OIL RESERVOIR INTO THE AIR CUSHION. 